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Topic Review (Newest First)

12-11-2012 10:17 AM

V8&4spd

Unhook the battery for a few hours. The computer should reset itself. The fuel line sounds like the main problem. Fresh plugs could not hurt. The fuel filter is inside the frame rails near the drivers seat area. If you remove the filter you should be able to blow air through it easy, you will be able to tell if it's clogged.

12-11-2012 12:32 AM

dsraven

one more thing, check the ground for the pump. also check the grounds from the battery to the body and the battery to the engine. check the harness ground points at the thermostat housing as well.

12-11-2012 12:28 AM

dsraven

trying to run the engine with starting fluid is not recomended.
find the fuel pump relay, on the firewall probably, and jumper it so the fuel pump will run when you want it to run. the grey wire goes to the fuel pump, the red wire is the fuel pump prime wire and if you power that up the fuel pump should turn on. the other end of the red wire should be somewhere near the brake booster. insert jumper wire there. the orange wire comes from the underhood fuse/relay box and should be hot at all times,it also heads over to the oil pressure switch to run the pump when the engine gets oil pressure if the relay craps out. if you can get the engine to run and you disconnect the fuel pump relay the engine should stay running if the oil pressure switch is good. the dark green/white is the wire that the computer powers up to turn on the relay, black/white is the ground to complete that turn on circuit. you can put a switch inline between the red and the grey for test purposes. this takes the relay out of the system and if you have some long wire it allows you to be under the truck and turn on/off the fuel pump. it comes in handy if you are alone when testing. now power up the fuel pump and test the fuel pump outlet pressure and see what you have. 9-13 psi is what it should be. next, remove the fuel filter and run the pump, catch the fuel in a container. that way you will know if it is actually pumping a volume of fuel up to the filter or if it just has some pressure but the volume drops off as soon as there is somewhere for it to go, like the engine started. like a pinched/restricted fuel supply line can do. then, if that is good, put the filter back on but don't connect the outlet fitting yet. retest the volume again. if the fuel filter passes the test then remove the return line and see what you have coming back from the throttle body with the pump running and the engine off.
is the fuel return line pinched anywhere?
have you checked the egr valve? remove it, place it upside down in a vice or something so the gasket surface is level and it can't move around. now pour some varsol or paint thinner into one of the ports. does it leak out into the other port or down the shaft from the diaphragm? if so, replace the egr valve because it is leaking exhaust into the intake system and leaning out the fuel mix, or it is leaking vacuum through where the rod goes to the diaphragm and that is leaning out the fuel mix.
have you tried plugging off all the vacuum lines to eliminate a possible leak from a brake booster or another accesory?
have you tested the ignition module? a bad module will usually retard the timing a bunch.
is the fuel pressure 9-13 psi? more than that could mean you have a restricted return line. if so, remove the return line and check the pressure again. if it is right after disconnecting the return line then check for a restricted return line.
lower than 9 psi could mean you have a bad regulator. if you have good pressure at the filter but not at the throttle body then it could be a pinched/restricted line from the filter to the throttle body.
did you check the injector filter screens?
did you check the injector rersistance? should be 1.3 ohms at 140degrees F. (unplug wiring harness so you are only testing the injector itself).
have you checked the idle air control valve? it is a resistance check across A to B and then C to D, should be 40-80 ohms. A to D and C to B should be infinite. if not passing these tests replace the iac. also check the port and the seat that the pintle goes into for dirt or debris.
have you checked the pcv valve operation, the supply hose and the port in the throttle body for blockage? it should be a wide open port to manifold vacuum. they are known for plugging up the passage in the throttle body. you have to take the throttle body off and flip it upside down to check it, then you might as well clean it while you are there. the pcvvalve should rattle when it is removed and shaken. check inside for gummy deposits that could hinder it's operation.
have you checked the map sensor? should have a 5 volt refernce supply. if you put 10 inches of vacuum on the port the voltage should drop 1-2.5 volts. grey should be reference, lt green is map sensor input to ecm, black is sensor voltage return. output is dependant on altitude and there is a chart for reference, but basically you should see a change when you put vacuum to the port. check for a plugged/cracked supply hose.
i would check the egr valve first, personally. if you have the proper fuel pressure and are getting a good cone of fuel at the injectors then there is probably a vacuum leak or the egr is leaking exhaust/vacuum into your intake.
hope this helps.
keep us posted

12-10-2012 10:25 PM

Pre-Tuner

Are you sure the pump is turning on? And runs during cranking?

The oil pressure switch will shut down the pump if you don't have oil pressure. Also, there is a relay on the firewall for the pump that might have given up the ghost. If the contacts inside are dirty, the pump may not operate (or operate very weak).

Just some thoughts since you replaced the pump and it still doesn't start.

12-10-2012 08:48 PM

millertime23

95 350 tbi

Alright well i dropped the gas tank, i found out that the little line between the pump was completely shot and cracked. So I replaced that and the fuel pump and strainer.
And i when I started it, it still did not run nor start up. Fired a bit but that's it.
I'm guessing I fouled a plug or something. So I'm going to replace the plugs tomorrow and hopefully it fixes it, if it doesn't thatn I'm at a dead end! Any other pointers would be great!

12-10-2012 04:22 PM

LATECH

10 PSI wont even budge the needle on that thing. Get online and find a 15 PSI gauge or forget it.
You absolutely CANNOT make real and proper assesment/diagnosis of fuel pressure without a gauge that has the correct range.
Look at this one, I have it and it works very wellSuper price on KD Tools 2521 at ToolTopia.com
It also doubles as a vacuum gauge, notice 15 Lbs and half the gauge for the sweep....Makes it pretty accurate

12-09-2012 07:19 PM

millertime23

95 350 tbi

The range was 0- 60 or 100 Ibelieve Icouldnt find one with only 0-20

12-09-2012 03:16 PM

LATECH

What range was the gauge?

12-09-2012 02:53 PM

millertime23

I put the fuel pressure gauge inline between the fuel filter, I came up with no pressure at all, and that was both, run, and start/cycling

12-09-2012 11:49 AM

V8&4spd

There is a small fuel line on the end of the fuel pump inside the gas tank. You might want to double check that. I had one swell up on me and there was a split in it that you could not see at first. I think the junk gas they sell now had something to do with it. If you drop the gas tank you might as well change the fuel pump while you are in there. That small rubber fuel line caused me all kinds of work.

12-09-2012 11:28 AM

millertime23

95 tbi 350 problems!

Alright thanks guys, I'm going to check fuel pressure first, so when Ihook up the gauge, inline it between the fuel filter, and if the pressure is not what it needs to be, Iwill drop the tank and replace the fuel pump, however Ido it.
Now could it possibly.be the fuel regulator? Because the injectors do spray a nice cone shape.

12-09-2012 09:09 AM

LATECH

Also, on a chevy, rather than wrestle with removing rusty tank straps, I remove the BED. It has 8 bolts , easy to remove, then the rear harness and ground lead back at the bumper, and the filler shroud at the side body panel. Get 3 friends to help lift it off. Leaves it wide open. Better than laying under a truck, eating dirt, rust and ultimately lifting 250 lbs of sloshing fuel in a tank

12-09-2012 09:06 AM

LATECH

I agree with GMC . Sounds like a fuel starvation/volume/pressure problem.
You will need a 15 -20 PSI gauge with a good sweep to be able to accurately read any discrepency in a 13 PSI system.
A 60 or 80 PSI gauge wont have enough incrementation for anyone to discern a problem or not.
You can remove the fuel filter outlet line and patch in at that point for your test fitting, it is way easier than trying to hump over the engine and fight the rigid lines in the back of the TBI been there done that.
For a test and short term operation, you wont need to use Fuel Injection line as the pressure is only going to be 11-13 PSI.
When you get it hooked up, start it run it , then replicate the operational condition which causes the symptom, the watch the gauge to see.
Check the specs for peak head pressure with engine off key on, engine running at idle, and engine running at acceleration( vacuum/regulator test) Good luck.

12-09-2012 08:47 AM

millertime23

95 tbi 350, will not run!

So the fuel pump can be bad even if it still kicks on and winds up? And when Iput the fuel pressure gauge in the lines, should Icut it in, where the fuel filter is? And its 9-13 psi right?

12-09-2012 08:41 AM

millertime23

So even though the fuel punk kicks on, could mean its bad?? And when i put the gauge on it, should i hook it to the fuel filter lines?

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